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Pilový kotouč v procesu podélného řezání materiálů na bázi dřeva
Veselý, Přemysl
In this dissertation thesis there is listed characteristics of circular saw blades, their distribution, influence of construction adjustments on final behavior of blade in the process of machining, problematic of oscillation of blades a mutual interaction among quality of machined surface, noise and dust. The thesis covers the problems of oscillation of circular saw blades as when idling and operating - the cutting process; and by the use of three circular saw blades with different construction modifications. These aforementioned construction measures are also compared to each other due to the implementation of standard construction saw blades not only from the perspective of oscillation, but also from the perspective of the roughness of the machined surface and the analysis of wood waste generated during cutting and noise. In the theoretical part there is an analysis of available literature and scientific theses. It outlines the particular publications devoted to methods of determining the shapes of oscillation, determining critical, resonant and recommended speed, blade constructions, including possible modifications, the theory of cutting saw blades including determining the size and shape of the splints and the effects of noise on the work environment. An important part of this work is methodology involving direct measurements for detection of unstable states of discs (resonance and critical speed. In this section it is further evaluated measuring of the oscillation of the test saw blade and verification of the proposed methodology with a different and practiced, commonly known method, so called cold shapes: The author also seeks to explore and determine the effect of different tooth pitch and method of execution of slots along with soundproofing grooves on noise levels, the resulting quality of the machined surface of various wood. The generated waste is then analyzed for splitting wood particles in particular size group with the percentage of each chip. The results of the experiment are in discussion confronted with the available scientific theses, taking into account with normal operating conditions, of which the conclusion is drawn.
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Analysis of transfer matrix method using for calculation of electrical machines rotor with influence of magnetic pull
Tobiáš, Jan ; Majer, Zdeněk (referee) ; Vlach, Radek (advisor)
This master thesis is dealing with modeling of the rotor system based on the numerical transfer matrix calculations. This method is suitable for fast analysis of beam bodies to observe the resulting deflection and critical speed in regard to the initial circumstances. The bearing stiffness is a significant input factor that affects the outcomes of the analysis, especially the critical speed the rotor system. First of all,the available approaches to analyze the bended beam bodies are discussed focused on explanation of the transfer matrix algorithm. After that, the approach to estimate the bearing stiffness based on the Hertz contact theory is presented. Further, a brief explanation is given about the heat arising in the rotor bearings. The following chapters are focused on description of the software solver for rotor system analysis based on the transfer matrix method, considering the bearing stiffness estimation based on Hertz contact theory, with possible calculations of the induced bearing heat losses. In the end, the practical use of the developed software is presented with the analysis of the obtained results of the rotor deflection, critical speed, and bearing power loss. There is also discussed a comparison of the different bearing stiffness estimation with the impact to the computation outcomes, especially on the rotor critical speed, followed by comparison conclusion implementation into rotor system analysis.
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Analysis of the rotor packet prestress on the rotor critical speed
Lekeš, Filip ; Huzlík, Rostislav (referee) ; Lošák, Petr (advisor)
The presented diploma thesis deals with the modeling of the rotor packet in dynamic calculations and analysis of the influence of the packing pressing force on the critical speed of the electric motor. The thesis can be divided into three main parts. The first part discusses the current level of rotor packet modeling in dynamic calculations and also deals with analytical theories for subsequent experimental tests. The second part describes the implementation of two experiments to determine the equivalent modulus of elasticity. The first experiment is a four-point bending test and the second is an experimental modal analysis. The third part is used for comparing the results obtained from experimental tests and describes the calculation of the critical speed of the rotor package pressed on the shaft by the finite element method.
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Design of high speed permanent magnet synchronous machine
Přibyl, Daniel ; Knebl, Ladislav (referee) ; Ondrůšek, Čestmír (advisor)
Bachelor's thesis is focused on problematic of synchronous machines with permanent magnets. In this thesis is described the principle of function and design solution of the machine. Furthermore it deals with stator winding, possibility of placing magnets on the rotor and used types of permanent magnets. In the part of solution of the assignment of work is made design of synchronous machine with permanent magnets with output 1,5 MW and rated speed 15000 rpm. The machine is designed with inner rotor and magnets placed on surface. The solution includes design of dimensions of stator including design of slot, design of winding and design of permanent magnet. The whole analytical design was finally compared with the results of the analysis in the RMxprt program. For machine was calculated 2D magnetic field by finite element method in Ansys Maxwell. Finally was calculated critical speed.
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Design of computational algorithm of electric machine rotor with respect to stress-strain relationships and critical speed
Pařízek, Daniel ; Lošák, Petr (referee) ; Vlach, Radek (advisor)
The Master's thesis deals with the mechanical design of electric machine rotor. Within the first two chapters of the practical part of the thesis two simplified computational models of the rotor (level 1 models) are compiled. Specifically, the model of flexible rotor mounted on rigid supports and model of rigid rotor mounted on flexible supports. The essence of these computational models lies in solvability using simple equations. Using these models can save time when constructing a pre-design of the rotor geometry. The following chapter is devoted to comparing different approaches to computational modeling of rotor using FEM. A predetermined preliminary design of a high-speed massive rotor is investigated. Computational models of different levels at stress-strain analysis and modal analysis are presented. It also includes a suggestion on how to proceed effectively in a given analysis.
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Pilový kotouč v procesu podélného řezání materiálů na bázi dřeva
Veselý, Přemysl
In this dissertation thesis there is listed characteristics of circular saw blades, their distribution, influence of construction adjustments on final behavior of blade in the process of machining, problematic of oscillation of blades a mutual interaction among quality of machined surface, noise and dust. The thesis covers the problems of oscillation of circular saw blades as when idling and operating - the cutting process; and by the use of three circular saw blades with different construction modifications. These aforementioned construction measures are also compared to each other due to the implementation of standard construction saw blades not only from the perspective of oscillation, but also from the perspective of the roughness of the machined surface and the analysis of wood waste generated during cutting and noise. In the theoretical part there is an analysis of available literature and scientific theses. It outlines the particular publications devoted to methods of determining the shapes of oscillation, determining critical, resonant and recommended speed, blade constructions, including possible modifications, the theory of cutting saw blades including determining the size and shape of the splints and the effects of noise on the work environment. An important part of this work is methodology involving direct measurements for detection of unstable states of discs (resonance and critical speed. In this section it is further evaluated measuring of the oscillation of the test saw blade and verification of the proposed methodology with a different and practiced, commonly known method, so called cold shapes: The author also seeks to explore and determine the effect of different tooth pitch and method of execution of slots along with soundproofing grooves on noise levels, the resulting quality of the machined surface of various wood. The generated waste is then analyzed for splitting wood particles in particular size group with the percentage of each chip. The results of the experiment are in discussion confronted with the available scientific theses, taking into account with normal operating conditions, of which the conclusion is drawn.
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Frequency analysis of the blades of the steam turbine impeller
Krejčí, Jaroslav ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The master thesis deals with modal analysis of the blade of the steam turbine impeller. This analysis is made to find the frequency response of the blade in order to predict the dangerous speeds of the steam turbine. At first the problem situation is described. Than follows the research study which is focused on steam turbines and especially on the rotor dynamic systems and the way to ascertain the modal parameters of the dynamic system by experiment. After that the solution of the problem is performed by computational modelling. The results of the computation are analyzed in detail for different variations of the blade length by Campbell diagram. A graph showing dependency between dangerous speeds of the turbine and the blade length is made out of the results. Then the results are verified by experiment and the coefficients of proportional damping are specified. In conclusion the optimal variation of the blade length for the given operational state is determined.
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Comparison of modal properties of steam turbine impeller with blades of different lengths
Havlásek, Michal ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The presented master's thesis deals with the safety assessment of several variants of the impeller with different blades length. The motivation for creating this thesis is to find the solution of the problem situation which is characterized by the breakdown of the steam turbine impeller with blades length of 30mm. As confirmed in this thesis, the impeller with blades length of 30mm is operated in the resonance. Likewise, according to the technical standard ČSN EN ISO 10437 its operation is not safe. As the correction action for the problem situation solving is proposed the prolongation of the impeller's blades. The safety is detected for six variants of impeller with dierent blades length. For each variant, there is executed a modal analysis and its results are drawn up into the Campbell diagram. On the basis of this diagram, the safety of individual components is evaluated. The last part of the masters thesis concerns with the examination of the influence of blades length on the modal properties of the impeller.
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Analysis of mechanical behaviour of synchronous generator
Donát, Martin ; Hadaš, Zdeněk (referee) ; Dušek, Daniel (advisor)
This Master’s thesis deals with analysis of mechanical behaviour of the synchronous generator and assessment of the possibility of reducing the mass of the frame of the generator. The aims of this work were: to perform the stress-strain analysis and modal analysis of the required model of the synchronous generator, to assessment influence of single part of the frame of the generator over its stiffness and design construction modification of the frame of the generator, which reduce its mass.
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